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Ceiling fan speed control

Discussion in 'Electronic Repair' started by Silver Surfer, Sep 12, 2006.

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  1. My fairly old ceiling fan needs a speed control switch replacement. It's a
    three-speed fan with a three wire switch. There are no capacitors; instead
    it appears to use some kind of smallish transformer looking device for speed
    control. My Googling to find what the circuit might look like has been
    fruitless. Can someone point me toward an educational source of speed
    control schemes for these fans or else explain to me how mine works?
     
  2. I'd guess a tapped inductor.
     

  3. You can buy a replacement at most larger hardware stores fairly
    cheap, probably for less that you could repair the bad one.. Usually,
    it is the switch contacts that fail. If the inductor fails, you'll
    smell burning shellac of Formvar insulation.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  4. zack

    zack Guest

    if its runs at high speed only control is
    burned out or open, if it runs high speed on
    all settings control is short out or burned out.
    you can replace them with a capacitor 3 speed
    control, ive done this to some fans.
    goto a electrical store to get them, some
    have the circuits with them to follow.
     
  5. Well, the change to a capacitor control has some appeal. I suspect that if
    I could find the right switch for this thing it would be as good as new.
    The replacement switches at the hardware store say they are for 3 or 4 wire
    applications; however, there is no drawing to show how to hook up the three
    wire system. All the combinations I've tried so far have yielded less than
    desirable results. It might be about time to trace all the wiring and try
    to figure out what makes it tick.

    Thanks to all who have responded.
     
  6. Update:

    The fan is working just swell now. Figured out that it does indeed use some
    kind of inductance control. The transformer looking thing had only three
    wires. The middle lead went to the motor main and start windings. First
    speed was one of the inductor legs in series with the motor. The next speed
    was the other leg, and the final speed was produced with both legs in
    parallel. The legs were not equal in resistance, thus I assumed they had
    different inductance.

    Could not find a speed control witch like the original three-wire one.
    Bought one of those two-layer 5 to 8 wire speed control switches and wired
    up all the contacts on the first layer and one of the contacts on the outer
    layer to get the equivalent contact sequence as the original switch.

    Are variable inductance speed controls like the one for my fan very common?
    What is their advantage?
     
  7. What else would you use?
     
  8. During my research into the problem the most common technique mentioned
    involved switching different valued capacitors in and out of the circuit.
    Not once did I encounter a variable inductance circuit.
     
  9. It's a cost/size trade-off. Until recently capacitors would have been too
    large or expensive or both. It seems this has changed.

    Most table/floor fans and many other appliances have the inductors 'built
    in' as part of the motor.
     
  10. Guest

    capacitor droppers are a bit more energy efficient, due to the R in
    wound inductors.

    NT
     
  11. Ian Jackson

    Ian Jackson Guest

    To reduce the noise of an extractor fan in the toilet, I've successfully
    slowed down by adding a series capacitor (rated at much more than mains
    voltage. I'm not sure what kind of fan it is, but it's probably an
    induction motor. However, the value of the capacitor is very critical.
    Too little, and it really slows down. Too much, and it runs up to full
    speed (as if the capacitor wasn't there). Any change of mains voltage is
    very apparent. The value of the capacitor has to be determined by trial
    and error.
    Ian.
    --
     
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